MySQL函数基础25字中文指南（mysql中函数基础入门）

MySQL函数基础：25字中文指南

MySQL是一种常用的关系型数据库管理系统，拥有丰富的函数库来方便开发者进行各种数据处理操作。本文将为大家提供一个MySQL函数25字中文指南，让你快速了解MySQL函数的基础用法。

1. AVG：计算平均值

SELECT AVG(score) FROM table;

2. CONCAT：合并字符串

SELECT CONCAT(firstname, , lastname) FROM table;

3. COUNT：计算行数

SELECT COUNT(*) FROM table;

4. DATE_FORMAT：格式化日期

SELECT DATE_FORMAT(date, %Y-%m-%d ) FROM table;

5. IF：条件判断

SELECT IF(score = 60, 及格 , 不及格 ) FROM table;

6. LENGTH：计算字符串长度

SELECT LENGTH(name) FROM table;

7. MAX：找出最大值

SELECT MAX(score) FROM table;

8. MIN：找出最小值

SELECT MIN(score) FROM table;

9. RAND：生成随机数

SELECT RAND() FROM table;

10. ROUND：四舍五入

SELECT ROUND(score, 2) FROM table;

11. SUBSTR：截取字符串

SELECT SUBSTR(name, 1, 3) FROM table;

12. SUM：计算总和

SELECT SUM(score) FROM table;

13. TRIM：去除空格

SELECT TRIM(name) FROM table;

14. UCASE：转换为大写

SELECT UCASE(name) FROM table;

15. LCASE：转换为小写

SELECT LCASE(name) FROM table;

16. NOW：获取当前时间

SELECT NOW() FROM table;

17. YEAR：获取年份

SELECT YEAR(date) FROM table;

18. MONTH：获取月份

SELECT MONTH(date) FROM table;

19. DAY：获取日期

SELECT DAY(date) FROM table;

20. CONCAT_WS：合并字符串并去掉空值

SELECT CONCAT_WS( , firstname, lastname) FROM table;

21. GROUP_CONCAT：按分组合并字符串

SELECT GROUP_CONCAT(name SEPARATOR , ) FROM table GROUP BY score;

22. IFNULL：替换空值

SELECT IFNULL(name, 未知 ) FROM table;

23. CASE：多条件判断

SELECT CASE WHEN score = 90 THEN 优秀 WHEN score = 60 THEN 及格 ELSE 不及格 END FROM table;

24. INSTR：查找字符串位置

SELECT INSTR(name, ll ) FROM table;

25. REPLACE：替换字符串

SELECT REPLACE(name, ll , rr ) FROM table;

以上25个MySQL函数基础指南可以让你更加熟练地使用MySQL进行数据处理，极大地提高你的开发效率。

代码演示：

SELECT AVG(score) FROM student;

SELECT CONCAT(firstname, , lastname) FROM student;

SELECT COUNT(*) FROM student;

SELECT DATE_FORMAT(date, %Y-%m-%d ) FROM student;

SELECT IF(score = 60, 及格 , 不及格 ) FROM student;

SELECT LENGTH(name) FROM student;

SELECT MAX(score) FROM student;

SELECT MIN(score) FROM student;

SELECT RAND() FROM student;

SELECT ROUND(score, 2) FROM student;

SELECT SUBSTR(name, 1, 3) FROM student;

SELECT SUM(score) FROM student;

SELECT TRIM(name) FROM student;

SELECT UCASE(name) FROM student;

SELECT LCASE(name) FROM student;

SELECT NOW() FROM student;

SELECT YEAR(date) FROM student;

SELECT MONTH(date) FROM student;

SELECT DAY(date) FROM student;

SELECT CONCAT_WS( , firstname, lastname) FROM student;

SELECT GROUP_CONCAT(name SEPARATOR , ) FROM student GROUP BY score;

SELECT IFNULL(name, 未知 ) FROM student;

SELECT CASE WHEN score = 90 THEN 优秀 WHEN score = 60 THEN 及格 ELSE 不及格 END FROM student;

SELECT INSTR(name, ll ) FROM student;

SELECT REPLACE(name, ll , rr ) FROM student;

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